Humans leave a frozen legacy of microbes on Mount Everest

Location of soil samples near South Col Camp

A camp on the South Col where hundreds of adventurers set up their last camp each year before attempting to scale the world’s highest peak from the south-eastern side. The photo was taken near where Baker Perry’s soil samples were collected. Photo credit: Baker Perry

Perched nearly 5 miles above sea level in the Himalayas, the barren, windswept dip between Mount Everest and its neighboring peak, Lhotse, remains snow-free. At the South Col, hundreds of thrill-seekers set up their last camp each year and prepare to scale the world’s highest mountain from the southeast flank.

New research led by the University of Colorado Boulder shows these adventurers inadvertently leave behind a frozen signature of resilient microbes. These microorganisms can endure extreme conditions at high altitudes and remain dormant in the soil for decades or possibly even centuries.

The research not only highlights an unseen tourism impact on the world’s highest mountain, but could also lead to a better understanding of the ecological limits of life on Earth and where life on other planets or cold moons might exist. The results were published in last month Arctic, Antarctic and Alpine researcha journal published on behalf of the Institute of Arctic and Alpine Research (INSTAAR) at CU Boulder.

“Even at this altitude, a human signature is frozen in Everest’s microbiome,” said Steve Schmidt, the paper’s senior author and professor of ecology and evolutionary biology.

For the past few decades, scientists have been unable to positively identify human-associated microbes in samples collected over 26,000 feet. This study marks the first time that next-generation gene sequencing technology has been used to analyze soil from such a high altitude on Mount Everest, allowing researchers to gain new insights into almost anything and everything found within .

Researchers were not surprised to find microorganisms left behind by humans. Microbes are everywhere, even in the air, and can easily fly around and land some distance from nearby camps or trails.

“If someone has just blown their nose or coughed, it can show,” said Schmidt.

What impressed them, however, was that certain microbes that evolved to thrive in warm and wet environments like our noses and mouths were resilient enough to survive in a dormant state in such harsh conditions.

life in the cryosphere

This team of CU Boulder researchers — including Schmidt, lead author Nicholas Dragone, and Adam Solon, both graduate students from the Department of Ecology and Evolutionary Biology and the Cooperative Institute for Research in Environmental Science (CIRES) — are studying the cryobiosphere: the Earth’s cold regions and the limits of life within them. They’ve sampled soil everywhere, from Antarctica and the Andes to the Himalayas and the high Arctic. Normally, microbes associated with humans do not occur at these sites to the extent that they have appeared in recent Everest samples.

Schmidt’s work over the years linked him to researchers who set out for Everest’s South Col in May 2019 to build the planet’s highest weather station established by the National Geographic and Rolex Perpetual Planet Everest Expedition.

He asked his colleagues: Would you mind collecting some soil samples while you’re there?

So co-author Baker Perry, professor of geography at Appalachian State University and National Geographic Explorer, hiked as far away from South Col Camp as possible to scoop up some soil samples and send them back to Schmidt.

Extremes on Earth and elsewhere

Dragone and Solon then analyzed the soil in several labs at CU Boulder. Using next-generation gene sequencing technology and more traditional cultivation techniques, they were able to identify the[{” attribute=””>DNA of almost any living or dead microbes in the soils. They then carried out extensive bioinformatics analyses of the DNA sequences to determine the diversity of organisms, rather than their abundances.

Most of the microbial DNA sequences they found were similar to hardy, or “extremophilic” organisms previously detected in other high-elevation sites in the Andes and Antarctica. The most abundant organism they found using both old and new methods was a fungus in the genus Naganishia that can withstand extreme levels of cold and UV radiation.

But they also found microbial DNA for some organisms heavily associated with humans, including Staphylococcus, one of the most common skin and nose bacteria, and Streptococcus, a dominant genus in the human mouth.

At high elevations, microbes are often killed by ultraviolet light, cold temperatures, and low water availability. Only the hardiest critters survive. Most—like the microbes carried up great heights by humans—go dormant or die, but there is a chance that organisms like Naganishia may grow briefly when water and the perfect ray of sunlight provides enough heat to help them momentarily prosper. But even for the toughest of microbes, Mount Everest is a Hotel California: “You can check out any time you like/ But you can never leave.”

The researchers don’t expect this microscopic impact on Everest to significantly affect the broader environment. But this work does carry implications for the potential for life far beyond Earth, if one day humans step foot on Mars or beyond.

“We might find life on other planets and cold moons,” said Schmidt. “We’ll have to be careful to make sure we’re not contaminating them with our own.”

Reference: “Genetic analysis of the frozen microbiome at 7900 m a.s.l., on the South Col of Sagarmatha (Mount Everest)” by Nicholas B. Dragone, L. Baker Perry, Adam J. Solon, Anton Seimon, Tracie A. Seimon and Steven K. Schmidt, 16 February 2023, Arctic, Antarctic, and Alpine Research.
DOI: 10.1080/15230430.2023.2164999

The study was funded by the National Geographic and Rolex Perpetual Planet Everest Expedition, the Department of Ecology and Evolutionary Biology, and the University of Colorado Boulder Libraries Open Access Fund


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